Light source



March 20, 1934. H. KUNEMANN LIGHT SOURCE Filed July 15, 1930 Patented Mar. 20, 1

LIGHT SOURCE I liieinrlch Kijnemann, Munster, Germany Application July 15, li'i30, Serial No. 468,085 In Germany July 6, 1929 2, Claims.

The invention relates to a device for recording sound waves on a movingphoto-sensitive support, uslng a tungsten are lamp as the source of light for recording, and provides an arrangement enabling a clearer sound record .to be obtained than heretofore. Y

The invention is based on the knowledge that the arc light of the tungsten arc'lamp possesses not merely a high photo chemical activity, but Ed has an extraordinary capacity for oscillating, and more particularly, is considerably freer from inertia than the remainder of the light emitted by the lamp, especially the light from the electrodes. For these reasons, by the means given here after, theinvention provides a way of eliminating the efiect of factors which interfere with the character of the arc as a pure arc.

'iwo constructional examples of recording devices according to the invention are shown in the 225i) drawing, in which:

1'1 1; i is a, longitudinal section of a soundcurrent modulated tungsten are lamp having a screened, pure are, and

e 2 is a section through a recording apparatus having the means for screening the said are situated in the optical arrangement.

It is well known to cause the light from a source of illumination to oscillate or fluctuate in rhythm with the sounds to be recorded, andto employ this light, by pamage through a narrow aperture, to efiect a photochemical change in the light-sensitive it nwhich moves past the aperture. According to the present invention, it isv proposed to employ a tungsten arc lamp, as .a source or m m: It has been found in practice that the records produced by such are lamps at times lacking in clearness, particularly withthe higher frequencies of sound vihrations.

According to the present invention, a distinction is made between the several sources of light present in a tungsten arc lamp, to-wit: electrodes and the arc itself. The electrodes are much slower in response to variations of current intensity by reason of inertia effects, as they are at the necessary velocity. On the other hand,

the-arc itself responds much more quickly and unable to become heated or to give off their heat arc, uneven heating of the electrode ends, which currentleads and electrode holders mounted in the glass base of the lamp, these parts being en closed from the atmosphere by the glass envelope 6.

Screens 7 and 8, located on the leads or holders 3 and 4 of the electrodes 1 and 2, serve to allow only the are light, coming from the are itself and capable of rapid oscillation "to issue from the vicinity of the arc and pass through the envelope 6. Thus, a bundle of light rays, representing only the are light, passes toward'the surface S which is to be illuminated, and may illuminate the same for the area indicated as L in Figure 1: while thelight emitted by the electrodes of the recording lamp, and thus being less capable of oscillation by reason of the inertia referred to above, is out ed by the screens 7 and 8 from passage to the surface S, and may onlypass outward from-the arc lamp in the directions marked L1 and L2 in Figure 1.

, The screens '7 and 8 may be combined to form a single, electrically non-conducting screen plate, which is provided with an aperture for the passage of the arc rays. Such a screen strengthens the two electrode holders 3, 4 in a very desirable manner and assists in maintaining the electrodes at a predetermined distance.

In-the optical arrangement shown dimatically in Figure 2, the tungsten arc lamp employed is absolutely identical with that shown in Figure 1, except that the screens 7 and 8 are omitted, so that all the light of the tungsten arc lamp is emitted freely. The condenser. 18 projects at the plane 12', 12' a complete image oi the recording lamp; a screen 12, fixed at this point, allows however only the light of the are, which is well capable of oscillating, to pass through the lens 11. The lens 11 therefore projects onto the film i4: at thepoint 15 an image of. the light of the are as it passes the narrow slot 13.

Instead of the method of screening shown, any other type of screening may be used, provided only that it is adapted to allow only the rays of light emitted by the arc, which is well capable of oscillating, to reach the photo-sensitive support.

In addition, the screening means serve towithhold other-disturbing factors: wandering of the disturb the homogeneity of the arc, and deviation of the are from the most favourable shape for recording.

- A chief means is to make'the electrodes of such a shape that their ends which are directed towards one another are each of the shape of a flat dome. Experiments have shown that by giving them this shape, the wandering of the arc and any uneven heating of the electrode ends may be excluded.

Ithas'also been found essential, in selecting the distance between the electrodes as well as thegas pressure prevailing in the lamp, to proceed from the point of view of obtaining a compact cylindrical shape of are. If the arc becomes constricted, or if it becomes very wide at the cathode and very narrow at the anode, it loses recording power. The best distance between the electrodes for a maximum current strength of 1 to 2 amperes, is about 3 mm. The pressure is about 150 mm. of mercury. These, however, are not sharply defined optima; more particularly, one precaution (distance or pressure) may be replaced to some extent by the other.

Y In order to fix undisplaceably the most favourable distance between the electrodes, once it has been ascertained, the electrode holders or leads I 3 and 4 are made of very robust dimensions. This obviates the danger of trembling of the electrode arms when the lamp receives shocks, which would disturb the distance between the electrodes and hence the continuity of the records? I claim:

1. Asource for producing rapidly varying degrees of illumination comprising a modulatable arc lamp having an enclosing envelop with electrode supports therein and tungsten electrodes on said supports, and screening means mounted on said supports within the envelop and in the path of the light emitted by the lamp for preventing the passage of light from the electrodes ,and permitting the passage of light from the arc itself.

,2. A source as in claim 1, in which the screening means. includes non-conductive material connected to said supports whereby the screening 

